A grandmother on death row in Indonesia has lost an appeal at the UK's highest court over the lawfulness of a Government policy not to provide funding for legal representation to Britons facing capital charges abroad.

Five Supreme Court justices in London unanimously dismissed a challenge by Lindsay Sandiford, 57, from Cheltenham, Gloucester, who was convicted last year of trafficking drugs into the resort island of Bali and sentenced to death by firing squad.

But the court pointed out that she remains in "jeopardy" and the evidence now called for a further urgent review of the policy in her case.

The judges were told at a hearing last month that she is effectively without legal representation in Indonesia to allow her to pursue a further hearing of her case, and has "no access to any further private funding".

Her QC Aidan O'Neill said that previously Sandiford had been able to fund her legal fight against the death sentence in the Indonesian courts through the "kindness of strangers".

Today's ruling by Lords Mance, Clarke, Sumption, Carnwath and Toulson follows a Court of Appeal defeat for Sandiford in April last year when three leading judges ruled that the UK Government's policy of not providing funding for legal representation to any British national who faced criminal proceedings abroad - even in death penalty cases - was not unlawful.

At the hearing of her appeal, Mr O'Neill told the Supreme Court: "The current situation of the appellant is that she has one last chance of seeking review or appeal through the courts against the death penalty being carried out on her - by way of application for judicial review to the Indonesian Supreme Court. This requires a detailed knowledge of Indonesian law."

There was also the possibility of her submitting a petition for clemency to the Indonesian government, which also "requires a close knowledge of the Indonesian judicial and political situation and environment".

He added: "The appellant is, however, effectively without legal representation in Indonesia to allow her to pursue this line of judicial review, and she has no access to any further private funding which might otherwise allow her to instruct a suitably qualified lawyer."

Last year's Court of Appeal ruling followed an earlier High Court decision that the Government was not legally obliged to pay for "an adequate lawyer" to represent Sandiford, who was sentenced to death by firing squad after being found with cocaine worth an estimated £1.6 million as she arrived in Bali on a flight from Bangkok, Thailand, in May 2012.

Appeal judges heard at the time of the hearing before them that she needed around £8,000 for her legal fight against the sentence.

Following those proceedings she received donations covering the sum needed.

Dismissing her challenge at the Court of Appeal, Master of the Rolls Lord Dyson said the question was not whether the Foreign Secretary could produce a different policy "which many would regard as fairer and more reasonable and humane than the present policy", but whether the policy he had produced was "irrational".

He concluded: "I am in no doubt that the policy is not irrational. It is based on reasoning which is coherent and which is neither arbitrary nor perverse."

Sandiford, originally from Redcar, Teesside - who claimed she was forced to transport the drugs to protect her children, whose safety was at stake - was sentenced to death in January 2013 by judges of the District Court of Denpasar in Bali.

She appealed but her case was rejected by the High Court of Denpasar.

Last August, a three-judge panel at the Indonesian Supreme Court in Jakarta also rejected her appeal.

In written submissions opposing Sandiford's appeal at the UK's Supreme Court last month, Martin Chamberlain QC, for the Foreign Secretary, said: "The death penalty is among the punishments to which the Government is opposed in all circumstances as a matter of principle."

It supported initiatives designed to encourage states which retained the death penalty to change their position and makes grants to charities such as Reprieve, which assisted individuals who were charged with capital offences.

In "appropriate cases" it also made "state to state representations".

Mr Chamberlain said the statutory legal aid scheme extended only to legal proceedings in the UK, and the Government "has not established an analogous scheme to cover legal expenses for British nationals involved in criminal proceedings abroad, even where the proceedings may result in the imposition of punishments to which it is strongly opposed".

He told the judges that the policy did not allow funding to be given, even in exceptional circumstances, but added: "However, that does not mean that the appellant's individual circumstances have been ignored."

Specific consideration was given to the question whether the policy should be changed in the light of those circumstances.

"The conclusion was that the appellant's case could not be regarded as more compelling than many others and that the policy should not be changed to allow payments in this case," he said.

The Supreme Court said Sandiford "now requires a substantial sum to pay for the legal assistance to prepare and present an application to the Indonesian Supreme Court to reopen the case and a clemency petition to the President of Indonesia".

The papers require to be lodged by August 29.

The judges said she remains in jeopardy and "urgently in need of legal help".

Lord Carnwath, announcing that the court "unanimously dismisses the appeal", added: "However, in the light of new information - not available to the lower courts - as to the course of the proceedings in Indonesia and the steps now available to her there, the court calls on the Secretary of State urgently to review the application of the policy to Mrs Sandiford's case in the light of that information."

In a written ruling, Lord Carnwath and Lord Mance said: "Since January 2013, as a result of the surprising course of the Indonesian proceedings, circumstances have radically developed in respects which appear to have been quite unforeseeable.

"However, we have no up to date information as to the department's consideration of those matters. As has been seen, those responsible have been willing to consider whether the policy should be departed from or qualified in her case, but that has been on information which is now out of date.

"Logic and consistency, if nothing else, call for an urgent review of the policy as it applies to her in the light of the current information."

They added: "The evidence now available as to the course of the Indonesian proceedings appears to raise the most serious issues as to the functioning of the local judicial system and its ability to deal justly with the appellant's case.

"In particular, on the material we have been shown, the local courts seem to have ignored the substantial mitigating factors in her case, including her age and mental problems, her lack of any previous record, her co-operation with the police and not least the remarkable disparity of her sentence with those members of the syndicate whom she helped to bring to justice."

They said: "On the face of it, there is substantial material to support her application to the Supreme Court or the President. She needs a competent lawyer to present it."

The judges said: "It is not, of course, for this court now to express any view as to what the outcome might be of such a review. But we note that, even under the old pre-2007 policy, it appears that the Foreign Office did not experience real difficulty in controlling and limiting the financial exposure which it incurred in a very few exceptional cases.

"It is not clear to us that the creation or recognition of an exception for a case as extreme as the present would risk opening a floodgate to future demands for financial support.

"However that may be, the further review needs to be undertaken, and the outcome to be supported by a clear justification of the rationality and/or proportionality of maintaining an absolutely blanket policy covering even the present circumstances."